Diagnosis
The thermostat has detected a heating or cooling cycle shorter than the minimum allowed time, which is 5 minutes by default. This protects your equipment.
How to Fix It
Check your air filter. A severely clogged filter is the most common cause. Replace it if dirty. Next, verify airflow: ensure all supply and return vents are open and unobstructed.
If That Didn't Work
The issue may be a faulty flame sensor (for gas heat) or a dirty outdoor unit (for AC/heat pump). For gas furnaces, cleaning the flame sensor with fine steel wool often resolves short cycling.
Heads Up
You can adjust the minimum cycle time in Menu > Installation > Thresholds > Minimum Cycle Time, but do not set it below 5 minutes. Adjusting this does not fix the underlying equipment problem.